USA TODAY - Scientists are still determining how much of Comet ISON survived its annihilating Thanksgiving journey around the sun, but they believe it's now probably "only dust," NASA said Monday.

"There's no doubt that the comet shrank in size considerably as it rounded the sun and there's no doubt that something made it out on the other side to shoot back into space," the agency wrote. "The question remains as to whether the bright spot seen moving away from the sun was simply debris, or whether a small nucleus of the original ball of ice was still there."

By Sunday, the remainder of the nucleus of the "comet of the century" was likely pulverized.

ISON's obituary was written after it passed within 684,000 miles of the sun Thursday, but images from the solar observatory released the next day showed some part of the 4.5-billion-year-old icy space rock heading back into space.

Confirming what exactly happened to ISON come later this month during observations by the Hubble Space Telescope.

Die-hard comet watchers will be eyeing the pre-dawn horizon later this week -- Friday or Saturday -- for any possible trace of ISON's zombie tail. But don't get your hopes up, Karl Battams of the Naval Research Laboratory warns in a question-laden eulogy -- with a final caveat.

"We all need to keep in mind how ISON keeps surprising us," he writes.